Superimposed telegraph circuits



May 13, 1930. R. v. MORGENSTERN SUPERIMPOSED TELEGRAPH CIRCUITS FiledMarch 5, 1928 hum iobzxz A FSQE zmPGm .535 uozw bum EZEuu Zmneutorfionald YMo qehs fem Patented May 13, 1930 UNITED STATES.

PATENT OFFICE RONALD V. MORGENSTERN, OF METUCHEN, NEW JEESEY, ASSIGNORTO THE WESTERN UNION TELEGRAPH COMPANY, OF NEW YORK, N. Y., ACORRORATION OF NEW YORK Application filed March 8,

This invention relates to superimposed circuits, particularly to-themethod of coupling the superimposed circuit to the circuit or on cuitson which it is superimposed.

The object of the invention is to provide a novel method of conductivelycoupling the superimposed circuit to the electrical center of the sourceof potential employed to send signalingcurrent over the circuit on whichup the superimposing is done. This condition 1s necessaryin'superimposed circuits in order that the circuit on which thesuperimposing is done shall not interfere with the superim osedcircuits.

t is also desired by this invention to pro vide the best possiblesuperimposed circuits with the least possible effect on the circuitsupon which they are superimposed.

The invention may be explained by reference to the accompanying drawingwhich shows the embodiment of the principles of the invention in asuperimposed telegraph system. In the system illustrated, two metallictelegraph circuits have superimposed on them a third metallic telegraphcircuit upon I which in turn is superimposed a ground return telegraphcircuit. In the telegraph system illustrated by the drawing, all thecircuits shown are arranged for the simultaneous. transmission ofsignals in opposite directions, but it is understood that the inventionis not to beconsidered as limited to such a system. On the figure theline conductors 11, 11 are used in a side circuit which is balanced forduplex operation by an artificial line 12, the

relay coils 13, 14, 15, 16 beingsuitably connected in such a way thatthe transmitter 17 at the same station does not produce actua tion ofthe relay. A similar arrangement is provided at the other terminal setof this side circuit, and at the terminal sets of the side gizr cuitwhich'includes line conductors 12, The relays at the terminal sets arepreferably so arranged that the coils which are con- SUPFEBIIMPOSEDTELEGRAPH CIRCUITS 1928. Serial No. 258,948

nected in the main line, e. g. coils 13 and 15, have twice the number ofturns of the coils in the artificial line, e. g. coils 14 and 16. Theadvantage of this arrangement is found in the fact that with a ivenwinding space on a relay it is possible %y this arrangement to secure agreater number of ampere turns to operate the relay than can be securedby making the artificial and main line coils contain the same number ofturns. This is explained in detail in' U. S. Patent No. 1,584,682 toAlbert Atherton' and George W. Janson.

The transmitter 17 is schematically represented by a tongue 18 havingalternate contacts which are connected to generators 19 and 20 forsupplying current impulses of o posite polarities to the line throughthe win ingsv of the receiving relay.

hen transmitting signals over the side circuit which includes conductors11, 11, current impulses of opposite polarities are sent to line rompotential sources 19 and 20 by way of tongue 18 and one or other of itscontacts. There is a tendency for current to flow through shunt 21 byreason of its connection across the two oints at which battery is aplied to the terminal set on the side circuit, ut this tendency isminimized because of the nature of the shunt. The inductance 22 andresistance 23 of the shunt are so regulated in relation to the constantsin the circuit that the shunting action of the shunt circuit at thebeginning of a signal is practically suppressed. It is not thereafterermitted to obtain a substantial value be orethe next current reversal.

The-conductors 24, 24 connect the midpoint a of inductive resistancecoils 22, 22 to the terminal set on the phantom circuit which is likethat provided at the terminals of each of the side circuits. Artificialline 32 balances for duplex operation the phantom circuit. The

transmitter 37, schematically represented as comprising a tongue 38 dida pair of contacts connected to potential sources 39 and 40, is

connected to the junction point of coils 33, 34, 35, 36 of the receivingrelay at the terminal set on the phantom circuit. A similar terminal setis provided at the other end of the phantom circuit. The main line coilsof these relays may, like those at the terminal sets of the sidecircuits, com rise twice as many turns as the correspon ing coils in theartificial line. In order to rovide a ground rev The inductiveresistance coil 26 is not inducreverses the polarity of the signalintive to currents originating at the terminals of the ground returncircuit, but is highly inductive to currents from the phantom circuit.

A conductor 28 leads from the electrical midpoint a of coil 26 to aterminal set 29 for the ground return circuit. The terminal set includesan artificial'line 30, relay-coils 31, 31 and a. transmitter connectedbetween ground and the junction of the relay coils and schematicallyrepresented as before, by a tongue and two cooperating contactsconnected to potential sources of opposite polarity. The operation ofthe system will be apparent from the following:

When transmission takes place over the side circuit comprisingconductors 11, 11, current impulses of opposite polarities are transmitted to line from sources 19 and 20 by way of tongue 18 and one or theother of its contacts. The shunt 21, by reason of its connection acrossthe terminals of the transmitter 17 tends to absorb part of the linecurrent, but this tendency is minimized because of the nature oftheshunt. The high inductance and the low resistance of the shunt are soregulated in relation to the constants of the circuit that the shuntingaction of the shunt circuit at the beginning of a signal is practicallysuppressed and is not thereafter permitted to attain a substantial valuebefore the next current reversal.

When the transmitter 17 at the terminal set the impedance oft e shunt isvery igh and allows a very small current to flow through it to thebattery return. This means that at the beginning of the signal there isa very small increase in the voltage drop across the resistance placedin the connection from potential sources 19, 20 to contacts oftransmitter 17,

due to the shunt on the battery su ply. .For

' this reason practically the same voltage is applied to the lineconductor at the beginning current,

of a signal as would be the case if this shunt was not present.

As the length of timeduring Which the same polarity of signaling currentis im pressed in the circuit increases the amount of current through theshunt increases, and the voltage across the resistance in the leads fromthe potential sources to the transmitter contacts alsoincreases,'lowering the potential applied to the line circuit. If theinductance of the shunt is high enough in relation to its resistance, i.e., if the time constant of the shunts is sufficiently great, thedistant receiving relay is reversed in response to the reversal ofsignaling current before there is any appreciable decrease in signalingcurrent strength, and the shorter the time length of signal the lessfinal effect the shunt will have in reducing the strength of thesignaling current. This is important because it is always the shortsignals which are the most diflicult totransmit over a circuit.

The same explanation applies to the action of shunt 25 in preventing anyappreciable effect of the hantom circuit transmitter upon thesuperlmposed circuit with ground return.

The resistance of the shunt can be made as small as is compatible withthe minimum voltage which must be applied to the line. The lower theshunt resistance the greater its time constant.

Since, the shunt is non-inductive to the superimposed currents, theimpedance which it offers to these currents is due only to itsresistance, which should be made as low as is practicable. It will be.further observed that the effective resistance which it ofiers to thesuperimposed current is equal to one-fourth the resistance oflered bythe shunt to the circuits on which the superimposing is done.

It is a parent that upon a judicious selection of t e values ofinductance and resistance of the shunt circuit depends the eflicien cywith which the desired results are attained. If the inductance of theshunt is of appropriate value compared to the rateof current reversal,the shunt circuit instead of absorbing, may even aid, by reason of thestored magnetic energy, in establishing the current reversal in theline.

The use of a single inductive resistance coil tapped at its center,rather than of two separate coils, offers the advantage of minimuminductive reactance to the currents from the superimposed circuit aswell as of maximum inductive reactance to current from the circuit uponwhich the superimposing is done.

In the example illustrated, the adjustable resistances 23 and 27 mayhave a value of 400 ohms; coils 13 and 15 may have 3500 turns and coils14 and 16, only 17 50' turns. Obviously, however, these values are givenmerely by way of example and may be varied widely to meet varyingcircuit conditions.

conductor of a circuit having a round re-' turn connected to themidpoint 6 said coil,

- whereby the inductance 0011 offers great.im-

connected to said conductor, w

tial connected to a pair pedance to the flow of current from the saidmetallic circuit and negligible impedance to flow from said groundreturn circuit.

2. The system according to claim 1, in which the resistance andinductance of the shunt circuit are adjusted in accordance with thevoltage of said source, the characteristics of the metallic circuit, andthe speed of signal transmission from said source to provideminimum'shunt eifect of the shunt circuit upon said source.

3. The method of operating a system according to claim 1 which comprisesregulating the relation of the speed of signal transmission to theconstants of the shunt circuit and of the metallic circuit so thatsubstantially the same volta e is applied to the metallic circuit at thebeginning of a signal as would be the case ifthe shunt were not present.

4:. A superimposed telegraph system, comprising a metallic circuit, 'asource of potenof terminals thereof, a shunt circuit connected to saidterminals and including an inductance and adjustable resistance, aconductor of a third circuit connected to the electrical center of saidshunt circuit, and a source of signalin potential hereby the shuntcircuit oifers great impedance to the flow of current from said metalliccircuit and negligible impedance to flow from said third circuitconductor.

5. The system according to claim 1, in which the resistance andinductance of the shunt circuit are adjusted in accordance with thevoltage of said source, the characteristics of the metallic circuit andthe speed of signal transmission of the metallic circuit and the speedof signal transmission from said source to provideminimumshunt efifectof the shunt circuit upon said source, the resistance of the shuntcircuit being made assmall as is compatible with the minimum voltagewhich must be applied to the line.

6. In a superimposed telegraph system, a pair of metallic side circuits,a source of plex operation,

potential for each side circuit connected to a pair of terminalsthereof, an inductive resistive shunt for each side circuit connected toa pair of terminals, a conductor of a phantom circuit connected acrossthe electrical centers of said shunt circuits, a source of potential forthe phantom circuit connected to said conductor, an inductive resistiveshunt connected across the terminals of said last I mentioned source,and a conductor for a transmlttmg cn'cuit connected to the electricalcenter of said last mentioned shunt.

7. In a superimposed telegraph system, a metallic side circuit, anartificial balancing line therefor, a pair of transmitting terminals forthe side circuit, a receiving relay comprisin coils connected betweeneach terminal and t e line conductor and between each terminal and theartificial line,- anda source of signaling currents connected to saidpair 'of terminals whereb signal currents from said source are ineective to operate said relay, a shunt circuit connected across said pairof terminals comprising a highly inductive resistance coil, and aconductor of a phantom circuit connected to an intermediate point ofsaid coil, whereby signal currents from said source have negligibleeffect upon said phantom circuit.

8. In a*superimposed telegraph system, metallic side circuit setsarranged for dusources of signaling poten tials connected to conjugatetransmittin terminals of said sets, a terminal set arrange for duplexoperation, and means connecting said sets to provide a phantom circuitfor said terminal set comprising shunt circuits connected .across theterminals of the signaling sources of said side circuit sets andincluding inductance coils so wound as to be noninductive to currentsfrom said phantom set and highly inductive to currents from said sidecircuit sets, whereby interference is prevented between the transmiitterof each set and'the receiver of its own or any other set.

9 In a telegraph system, a transmission line, a terminal set adapted forconnection to said transmission line, an artificial line for balancingsaid line with respect to transmitted current from said terminal set, ahighly inductive shunt circuit connected across the conjugatetransmitting terminals of said set, duplicate apparatus at the other endof the transmission line, and means connected to the electrical centersof said shunt circuits for completing a'superimposed circuit over saidtransmission line.

10. In a superimposed telegraph system, a pair of side circuits eachcomprising a source of si al' potentials connected to a pair oftermlnals t ereof, a phantom circuit including a source of signalingpotentials directly connected-to said side circuits and means in saidphantom circuit connection for preventing interference in said phantomcircuit from said side circuit signaling sources, said means comprisingan inductance coil in shunt to the terminals of each source, a groundedcircuit superimposed upon said phantom circuit and a means in-theconnection ofsaid grounded circuit for preventing interference from thephantom circuit in said grounded circuit, said last mentioned meanscomprising an inductance coil in shunt to the phantom circuit signalingsources.

In testimon whereof-I affix my signature.

RONXLD V. MORGENSTERN.

